PA Intermodulation Distortion Measurements Using the PNA

María Jesús Cañavate Sánchez

Index

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1. Introduction: characterization of a power amplifier

2. PNA N5225A

3. S-Parameters

4. AM/AM

5. AM/PM

6. Two-tone test

1. Introduction: characterization of a power amplifier

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S-Parameters

DUT: Amplifier

1. Introduction: characterization of a power amplifier

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Nonlinear characteristic

AM/AM and AM/PM compression

of a typical Traveling Wave Tube

(TWT) amplifier.

1. Introduction: characterization of a power amplifier

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Intermodulation distortion

DUT: Amplifier

Frequency spectrum of the amplifier

input signal: 5 unmodulated carriers.

AM/AM and AM/PM compression

of a typical Traveling Wave Tube

(TWT) amplifier.

Frequency spectrum of the amplifier

output signal: 5 unmodulated

carriers and IMP3.

2. PNA N5225A

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- Number of ports: 4

- Frequency range: 10MHz – 50GHz

- Max. port power, 20GHz: +13dBm

- Receiver damage level: +15dBm

2. PNA N5225A

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Damage: +15dBm

Damage: +30dBm

Damage: +43dBm

Coupling factor: 15dB

3. S-Parameters

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Power flow analysis (for all types of PA measurements)

3. S-Parameters

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Before calibration: make sure settings are at desired levels

3. S-Parameters

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Select power and internal attenuators levels

- Output power: -10 dBm

- Gain: 26 dB

- External attenuation: 6 dB

- Internal attenuation: 15 dB

- Measured S21 drops by the attenuation

- After calibration, attenuator losses will

be removed

- Before calibration: Gain = 5 dB

- After calibration: Gain = 26 dB

- Internal attenuation still not available

3. S-Parameters

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Calibration performance (for all types of PA measurements)

Source–power calibration at the input point of the amplifier

To ensure a constant and known power

Material needed: power sensor

Two-port SOLT calibration

To remove effects of the external and internal attenuators

Material needed: mechanical calibration kit

SOLT: short-open-load-through

3. S-Parameters

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Calibration performance

Source–power calibration Two-port calibration

3. S-Parameters

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Measurements

4. AM/AM

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S21 measurement under a power sweep condition

- Attenuator settings are fixed

- Source-power calibration at

source and receiver ports

4. AM/AM

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S21 measurement example

Gain

AM/AM

5. AM/PM

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Procedure:

S21 measurement under a power sweep condition

(AM/AM).

Change the S21 measurement from log magnitude format

to phase format.

No new calibration is required.

6. Two-tone test

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2 different configurations (option 087):

Using internal PNA components

Only extra cables are required

Using external components

Combiner

Coupler

Extra cables

6. Two-tone test

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Using internal PNA components:

6. Two-tone test

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Using external components:

6. Two-tone test

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6. Two-tone test

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Frequency tab:

6. Two-tone test

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Power tab:

Thank you!

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PhD student: María Jesús Cañavate Sánchez // mjc31@hw.ac.uk